Genes coding for flavone synthases

ABSTRACT

DNA obtained, for example, from snapdragon or torenia, encoding an enzyme that can convert flavanones directly to flavones, and its uses; the DNA and amino acid sequences for enzymes encoded thereby are listed as SEQ.ID. No. 1 &amp; 2 and 3 &amp; 4, for example. Introduction of the genes into plants can, for example, alter the flower colors of the plants.

This application claims priority under 35 U.S.C. §§119 and/or 365 to JP11-22427 and JP 11-205229, filed in Japan on Jan. 29, 1999 and Jul. 19, 1999, respectively; and a Continuation of PCT/JP00/00490 and a Continuation of PCT/JP00/04379, filed in WIPO on Jan. 28, 2000 and Jun. 30, 2000, respectively; the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to the control and utilization of biosynthesis of flavones, which have effects on flower color, protection from ultraviolet ray, symbiosis with microorganisms, etc. in plants, by a genetic engineering technique. More specifically, it relates to genes encoding proteins with activity of synthesizing flavones from flavanones, and to their utilization.

BACKGROUND ART

The abundance of different flower colors is one of the pleasant aspects of life that enriches human minds and hearts. It is expected to increase food production to meet future population increase by the means of accelerating the growth of plants through symbiosis with microorganisms, or by increasing the number of nitrogen-fixing leguminous bacteria, thus improving the plant productivity as a result of increasing the content of nitrogen in the soil. Elimination or reduction of the use of agricultural chemicals is also desirable to achieve more environmentally friendly agriculture, and this requires improvement of the soil by the abovementioned biological means, as well as higher resistance of plants against microbial infection. Another desired goal is to obtain plants with high protective functions against ultraviolet rays as a means of protecting the plants from the destruction of the ozone layer.

“Flavonoid” is a general term for a group of compounds with a C6-C3-C6 carbon skeleton, and they are widely distributed throughout plant cells. Flavonoids are known to have such functions as attracting insects and other pollinators, protecting plant from ultraviolet rays, and participating in interaction with soil microorganisms (BioEssays, 16 (1994), Koes at al., p.123; Trends in Plant Science, 1 (1997), Shirley, B. W., p.377).

Of flavonoids, flavone plays an important role in interaction of plants with microorganisms, especially in legumes, where they participate in the initial steps of the symbiosis with leguminous bacteria (Plant Cell, 7 (1995), Dixon and Paiva, p.1085; Annu. Rev. Phytopathol., 33 (1995), Spaink, p.345). Flavones in petals play a role in recognition by insects and act as copigments which form complexes with anthocyanins. (Gendai Kagaku, (May, 1998), Honda and Saito, p.25; Prog. Chem. Org. Natl. Prod., 52 (1987), Goto, T., p.114). It is known that when flavone forms a complex with anthocyanin, the absorption maximum of the anthocyanin shifts toward the longer wavelength, i.e. toward blue.

The biosynthesis pathways for flavonoids have been widely studied (Plant Cell, 7 (1995), Holton and Cornish, p.1071), and the genes for all of the enzymes involved in the biosynthesis of anthocyanidin 3-glucoside and flavonol, for example, have been isolated. However, the genes involved in the biosynthesis of flavones have not yet been isolated. The enzymes that synthesize flavones include those belonging to the dioxygenase family that depends on 2-oxoglutaric acid (flavone synthase I) and monooxygenase enzymes belonging to the cytochrome P450 family (flavone synthase II). These groups of enzymes are completely different enzymes with no structural homology.

It has been reported that in parsley, 2-oxoglutaric acid-dependent dioxygenase catalyzes a reaction which produces apigenin, a flavone, from naringenin, a flavanone (Z. Naturforsch., 36c (1981), Britsch et al., p.742; Arch. Biochem. Biophys., 282 (1990), Britsch, p.152). The other type, flavone synthase II, is known to exist in snapdragon (Z. Naturforsch., 36c (1981), Stotz and Forkmann, p.737) and soybean (Z. Naturforsch., 42c (1987), Kochs and Grisebach, p.343; Planta, 171 (1987), Kochs et al., p.519). A correlation has been recently reported between a gene locus and flavone synthase II activity in the petals of gerbera (Phytochemistry, 49 (1998), Martens and Forkmann, p.1953). However, there are no reports that the genes for these flavone synthases I and II were isolated or that flavone synthase II was highly purified.

The properties of a cytochrome P450 protein, which had licodione-synthesizing activity that was induced when cultured cells of licorice (Glycyrrhiza echinata) were treated with an elicitor, were investigated. The protein is believed to catalyze the hydroxylation of 2-position of liquiritigenin which is a 5-deoxyflavanone, followed by non-enzymatic hemiacetal ring opening to produce licodione (Plant Physiol., 105 (1994), Otani et al., p.1427). For cloning of licodione synthase, a cDNA library was prepared from elicitor-treated Glycyrrhiza cultured cells, and 8 gene fragments encoding cytochrome P450 were cloned (Plant Science, 126 (1997), Akashi et al., p.39).

From these fragments there were obtained two different full-length cDNA sequences, each encoding a cytochrome P450, which had been unknown until that time. Specifically, they were CYPGe-3 (cytochrome P450 No.CYP81E1) and CYPGe-5 (cytochrome P450 No.CYP93B1, hereinafter indicated as CYP93B1) (Plant Physiol., 115 (1997), Akashi et al., p.1288). By further expressing the CYP93B1 cDNA in a system using cultured insect cells, the protein derived from the gene was shown to catalyze the reaction synthesizing licodione from liquiritigenin, a flavanone, and 2-hydroxynaringenin from naringenin, also a flavanone.

2-Hydroxynaringenin was converted to apigenin, a flavone, by acid treatment with 10% hydrochloric acid (room temperature, 2 hours). Also, eriodictyol was converted to luteolin, a flavone, by reacting eriodictyol with microsomes of CYP93B1-expressing yeast followed by acid treatment. It was therefore demonstrated that the cytochrome P450 gene encodes the function of flavanone 2-hydroxylase activity (FEBS Lett., 431 (1998), Akashi et al., p.287). Here, production of apigenin from naringenin required CYP93B1 as well as another unknown enzyme, so that it was concluded that a total of two enzymes were necessary.

However, no genes have yet been identified for enzymes with activity of synthesizing flavones (such as apigenin) directly from flavanones (such as naringenin) without acid treatment. Thus, despite the fact that flavones have numerous functions in plants, no techniques have yet been reported for controlling their biosynthesis in plants, and improving the biofunctions in which flavones are involved, such as flower color. The discovery of an enzyme which by itself can accomplish synthesis of flavones from flavanones and acquisition of its gene, and introduction of such a gene into plants, would be more practical and industrially applicable than the introduction into a plant of genes for two enzymes involved in the synthesis of flavones from flavanones.

DISCLOSURE OF THE INVENTION

It is an aim of the present invention to provide flavone synthase genes, preferably flavone synthase II genes, and more preferably genes for flavone synthases with activity of synthesizing flavones directly from flavanones. The obtained flavone synthase genes may be introduced into plants and over-expressed to alter flower colors.

Moreover, in the petals of flowers that naturally contain large amounts of flavones, it is expected that controlling expression of the flavone synthase genes by an antisense method or a cosuppression method can also alter flower colors. Also, expression of the flavone synthase genes in the appropriate organs, in light of the antibacterial activity of flavones and their interaction with soil microorganisms, will result in an increase in the antibacterial properties of plants and improvement in the nitrogen fixing ability of legumes due to promoted symbiosis with rhizosphere microorganisms, as well as a protective effect against ultraviolet rays and light.

The present invention therefore provides genes encoding proteins that can synthesize flavones directly from flavanones. The genes are, specifically, genes encoding flavone synthase II that can synthesize flavones from flavanones by a single-enzyme reaction (hereinafter referred to as “flavone synthase II”).

More specifically, the present invention provides genes encoding P450 proteins having the amino acid sequences listed as SEQ.ID. No. 2, 4 or 8 of the Sequence Listing and possessing activity of synthesizing flavones from flavanones, or genes encoding proteins having amino acid sequences modified by additions or deletions of one or more amino acids and/or a substitution with different amino acids in said amino acid sequence, and possessing activity of synthesizing flavones from flavanones.

The invention further provides a gene encoding proteins having amino acid sequences with at least 55% identity with the amino acid sequences listed as SEQ.ID. No. 2, 4 or 8 of the Sequence Listing and possessing activity of synthesizing flavones from flavanones.

The invention still further provides genes encoding proteins possessing activity of synthesizing flavones from flavanones, and hybridizing with all or a part of the nucleotide sequences listed as SEQ.ID. No. 1, 3 or 7 of the Sequence List under the conditions of 5×SSC, 50° C.

The invention still further provides a vector, particularly an expression vector, containing any one of the aforementioned genes.

The invention still further provides a host transformed with the aforementioned vector.

The invention still further provides a protein encoded by any of the aforementioned genes.

The invention still further provides a process for producing the aforementioned protein which is characterized by culturing or growing the aforementioned host, and collecting the protein with flavone-synthesizing activity from the host.

The invention still further provides a plant into which any one of the aforementioned genes has been introduced, or progenies of the plant or a tissue thereof, such as cut flowers, which exhibit the same properties.

The invention still further provides a method of altering amounts and compositions of flavonoid using the aforementioned genes; a method of altering amounts of flavones using the aforementioned genes; a method of altering flower colors using the aforementioned genes; a method of bluing the color of flowers using the aforementioned genes; a method of reddening the color of flowers using the aforementioned genes; a method of modifying the photosensitivity of plants using the aforementioned genes; and a method of controlling the interaction between plants and microbes using the aforementioned genes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chromatogram showing the results of HPLC analysis of products obtained from a substrate, naringenin, using proteins encoded by CYP93B1 and TFNS5.

A and B: Obtained by adding a crude enzyme fraction of CYP93B1-expressing yeast.

C and D: Obtained by adding a crude enzyme fraction of TFNS5-expressing yeast.

A and C: Direct products obtained by addition of enzyme fraction.

B: Products obtained by acid treatment after reaction of A.

D: Products obtained by acid treatment after reaction of C.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Flavanone 2-hydroxylase encoded by the Glycyrrhiza CYP93B1 gene produces 2-hydroxyflavanones from flavanones as the substrates, and the products are converted to flavones by acid treatment. The present inventors viewed that it would be possible to obtain a gene encoding a flavone synthase II, which was an object of the invention, by using the Glycyrrhiza-derived cDNA, CYP93B1 for screening of a cDNA library of, for example, a flower containing a large amount of flavones, to thus obtain cDNA encoding proteins with activity of synthesizing flavones directly from flavanones as substrates.

According to the invention, a cDNA library of snapdragon which contains a large amount of flavones is screened using the Glycyrrhiza-derived cDNA, CYP93B1 as a probe, to obtain cDNA encoding a novel cytochrome P450 (see Example 1). The snapdragon cDNA, ANFNS2, obtained in this manner and the Glycyrrhiza CYP93B1 cDNA were then used as a mixed probe to obtain TFNS5, a cDNA encoding a novel cytochrome P450, from a cDNA library of torenia flower petals (see Example 2).

The torenia-derived cDNA was expressed in yeast and reacted with naringenin, a flavanone, as a substrate which resulted in production not of 2-hydroxynaringenin but rather of the flavone apigenin, without acid treatment (see Example 3). In other words, this enzyme directly produced flavones from flavanones without acid treatment, and its gene was confirmed to be a flavone synthase II which had never been cloned. The amino acid sequence encoded by the snapdragon-derived ANFNS2 of Example 1 exhibited high identity of 77% with the flavone synthase II encoded by TFNS5, and it exhibited the enzyme activity of flavone synthase II (Example 4). In addition, since an amino acid sequence encoded by perilla-derived cDNA also exhibited high identity of 76% and 75% with TFNS5 and ANFNS2, respectively (Example 8), it is speculated that the protein encoded by this cDNA also possesses the same enzymatic activity as the flavone synthases encoded by TFNS5 and ANFNS2.

The genes of the present invention may be, for example, one encoding the amino acid sequences listed as SEQ.ID. No. 2, 4 or 8 of the Sequence Listing. However, it is known that proteins whose amino acid sequences are modified by additions or deletions of multiple amino acids and/or substitutions with different amino acids can maintain the same enzyme activity as the original protein. Consequently, proteins having the amino acid sequences listed as SEQ.ID. No. 2, 4 or 8 of the Sequence Listing wherein the amino acid sequence is modified by additions or deletions of one or more amino acids and/or substitutions with different amino acids, and genes encoding those proteins, are also encompassed by the present invention so long as they maintain the activity of producing flavones directly from flavanones.

The present invention also relates to genes that have the nucleotide sequences listed as SEQ.ID. Nos. 1, 3 and 7 and nucleotide sequences encoding the amino acid sequences listed therein, or that hybridize with portions of their nucleotide sequences under conditions of 5×SSC, 50° C., for example, providing they encode proteins possessing activity of producing flavones from flavanones. The suitable hybridization temperature will differ depending on nucleotide sequences and the length of nucleotide sequences, and for example, when the probe used is a DNA fragment comprising 18 bases coding for 6 amino acids, the temperature is preferably not higher than 50° C.

A gene selected by such hybridization may be a naturally derived one, such as a plant-derived gene, for example, a gene derived from snapdragon, torenia or perilla; it may also be a gene from another plant, such as gentian, verbena, chrysanthemum, iris, or the like. A gene selected by hybridization may be cDNA or genomic DNA.

The invention also relates to genes encoding proteins that have amino acid sequences with identity of at least 55%, preferably at least 70%, such as 80% or greater and even 90% or greater, with any one of the amino acid sequences listed as SEQ.ID. Nos. 2, 4 or 8 of the Sequence Listing, and that possess activity of synthesizing flavones from flavanones.

A gene with the natural nucleotide sequence can be obtained by screening of a CDNA library, for example, as demonstrated in detail in the examples. DNA encoding enzymes with modified amino acid sequences can be synthesized using common site-directed mutagenesis or a PCR method, using DNA with a natural nucleotide sequence as a starting material. For example, a DNA fragment into which a modification is to be introduced may be obtained by restriction enzyme treatments of natural cDNA or genomic DNA and then used as a template for site-directed mutagenesis or PCR using a primer having the desired mutation introduced therein, to obtain a DNA fragment having the desired modification introduced therein. Mutation-introduced DNA fragments may then be linked to a DNA fragment encoding another portion of a target enzyme.

Alternatively, in order to obtain DNA encoding an enzyme consisting of a shortened amino acid sequence, for example, DNA encoding an amino acid sequence which is longer than the aimed amino acid sequence, such as the full length amino acid sequence, may be cut with desired restriction endonucleases, and if the DNA fragment obtained thereby does not encode the entire target amino acid sequence, it may be linked with synthesized DNA comprising the rest of the sequence.

Thus obtained genes may be expressed in an expression system using E. coli or yeast and its enzyme activity measured to confirm that the obtained gene encodes flavone synthase. By expressing the gene, it is also possible to obtain the flavone synthase protein as the gene product. Alternatively, it is also possible to obtain a flavone synthase protein even using antibodies for a full or a partial amino acid sequence listed as SEQ.ID. No. 2, 4 or 8, and such antibodies may be used for cloning of a flavone synthase gene in another organism.

Consequently, the invention also relates to recombinant vectors, and especially expression vectors, containing the aforementioned genes, and to hosts transformed by these vectors. The hosts used may be prokaryotic or eukaryotic organisms. Examples of prokaryotic organisms that may commonly be used as hosts include bacteria belonging to the genus Escherichia, such as Escherichia coli, and microorganisms belonging to the genus Bacillus, such as Bacillus subtilis.

Examples of eukaryotic hosts that may be used include lower eukaryotic organisms, for example, eukaryotic microorganisms, for example, Eumycota such as yeast and filamentous fungi. As yeast there may be mentioned microorganisms belonging to the genus Saccharomyces, such as Saccharomyces cerevisiae, and as filamentous fungi there may be mentioned microorganisms belonging to the genus Aspergillus, such as Aspergillus oryzae and Aspergillus niger and microorganisms belonging to the genus Penicillium. Animal cells and plant cells may also be used, the animal cells being cell lines from mice, hamsters, monkeys or humans. Insect cells, such as silkworm cells, or the adult silkworms themselves, may also be used.

The expression vectors of the invention will include expression regulating regions such as a promoter and a terminator, a replication origin, etc., depending on the type of hosts into which they are to be introduced. Examples of promoters for bacterial expression vectors which may be used include conventional promoters such as tac promoter, tac promoter, lac promoter, etc., examples of yeast promoters that may be used include glyceraldehyde-3-phosphate dehydrogenase promoter, PH05 promoter, etc., and examples of filamentous fungi promoters that may be used include amylase promoter, trpC, etc. Examples of animal cell host promoters that may be used include viral promoters such as SV40 early promoter, SV40 late promoter, etc.

The expression vector may be prepared according to a conventional method using restriction endonucleases, ligases and the like. The transformation of a host with an expression vector may also be carried out according to conventional methods.

The hosts transformed by the expression vector may be cultured, cultivated or raised, and the target protein may be recovered and purified from the cultured product, etc. according to conventional methods such as filtration, centrifugal separation, cell crushing, gel filtration chromatography, ion-exchange chromatography and the like.

The present specification throughout discusses flavone synthases II derived from snapdragon, torenia and perilla that are capable of synthesizing flavones directly from flavanones, and it is also known that the cytochrome P450 genes constitute a superfamily (DNA and Cell Biology, 12 (1993), Nelson et al., p.1) and that cytochrome P450 proteins within the same family have 40% or greater identity in their amino acid sequences while cytochrome P450 proteins within a subfamily have 55% or greater identity in their amino acid sequences, and their genes hybridize to each other (Pharmacogenetics, 6 (1996), Nelson et al., p.1).

For example, a gene for flavonoid 3′,5′-hydroxylase, which was a type of cytochrome P450 and participated in the pathway of flavonoid synthesis, was first isolated from petunias (Nature, 366 (1993), Holton et al., p.276), and the petunia flavonoid 3′,5′-hydroxylase gene was used as a probe to easily isolate a flavonoid 3′,5′-hydroxylase gene from gentian (Plant Cell Physiol., 37 (1996), Tanaka et al., p.711), prairie-gentian, bellflower (WO93/18155 (1993), Kikuchi et al.), lavender, torenia and verbena (Shokubutsu no Kagaku Chosetsu, 33 (1998), Tanaka et al., p.55).

Thus, a part or all of any of the flavone synthase II genes of the invention derived from snapdragon, torenia or perilla, which are capable of synthesizing flavones directly from flavanones, can be used as a probe, in order to obtain flavone synthase II genes capable of synthesizing flavones directly from flavanones, from different species of plants. Furthermore, by purifying the snapdragon-, torenia- or perilla-derived flavone synthase II enzymes described in this specification which can synthesize flavones directly from flavanones, and obtaining antibodies against the enzymes by conventional methods, it is possible to obtain different flavone synthase II proteins that react with the antibodies, and obtain genes coding for those proteins.

Consequently, the present invention is not limited merely to snapdragon-, torenia- or perilla-derived genes for flavone synthases II capable of synthesizing flavones directly from flavanones, but further relates to flavone synthases II derived from numerous other plants, which are capable of synthesizing flavones directly from flavanones. The sources for such flavone synthase II genes may be, in addition to snapdragon, torenia and perilla described here, also gentian, verbena, chrysanthemum, iris, commelina, centaurea, salvia, nemophila and the like, although the scope of the invention is not limited to these plants.

The invention still further relates to plants whose colors are modified by introducing a gene or genes for flavone synthases II that can synthesize flavones directly from flavanones, and to progenies of the plants or their tissues, which may also be in the form of cut flowers. By using the flavone synthases II or their genes which have been cloned according to the invention, it is possible to produce flavones in plant species or varieties that otherwise produce little or absolutely no flavones. By expressing the flavone synthase II gene or the genes in flower petals, it is possible to increase the amount of flavones in the flower petals, thus allowing the colors of the flowers to be modified toward the blue, for example.

Conversely, by repressing synthesis of flavones in flower petals, it is possible to modify the colors of the flowers toward the red, for example. However, flavones have myriad effects on flower colors, and the changes in flower colors are therefore not limited to those mentioned here. With the current level of technology, it is possible to introduce a gene into a plant and express the gene in a constitutive or tissue-specific manner, while it is also possible to repress the expression of a target gene by an antisense method or a cosuppression method.

As examples of transformable plants there may be mentioned rose, chrysanthemum, carnation, snapdragon, cyclamen, orchid, prairie-gentian, freesia, gerbera, gladiolus, baby's breath, kalanchoe, lily, pelargonium, geranium, petunia, torenia, tulip, rice, barley, wheat, rapeseed, potato, tomato, poplar, banana, eucalyptus, sweet potato, soybean, alfalfa, lupin, corn, etc., but there is no limitation to these.

Because flavones have various physiological activities as explained above, they can impart new physiological activity or economic value to plants. For example, by expressing the gene to produce flavones in roots, it is possible to promote growth of microorganisms that are beneficial for the plant, and thus promote growth of the plant. It is also possible to synthesize flavones that exhibit physiological activity in humans, animals or insects.

EXAMPLES

The invention will now be explained in further detail by way of the following examples. Unless otherwise specified, the molecular biological methods were carried out according to Molecular Cloning (Sambrook et al., 1989).

Example 1 Cloning of Snapdragon Flavone Synthase II Gene

RNA was extracted from about 5 g of young buds of a Yellow Butterfly snapdragon (commercial name by Sakata-no-Tane, KK.), and polyA+ RNA was obtained by an Oligotex. This polyA+ RNA was used as a template to prepare a cDNA library using a Lambda ZAPII cDNA Library Synthesis Kit (Stratagene) by the method recommended by Stratagene (Stratagene Instruction Manual, Revision #065001). The cDNA library was screened using the full length cDNA CYP93B1 as the probe. The screening and detection of positive clones were carried out using a DIG-DNA-labeling and detection kit (Boehringer) based on the method recommended by the same company, under a low stringent condition.

Specifically, a hybridization buffer (5×SSC, 30% formamide, 50 mM sodium phosphate buffer (pH 7.0), 1% SDS, 2% blocking reagent (Boehringer), 0.1% lauroylsarcosine, 80 μg/ml salmon sperm DNA) was used for prehybridization at 42° C. for 2 hours, after which the DIG-labeled probe was added and the mixture was kept overnight. The membrane was rinsed in 5×SSC rinsing solution containing 1% SDS at 65° C. for 1.5 hours. One positive clone was obtained, and it was designated as ANFNS1. Upon determining the nucleotide sequence at the 5′ end of ANFNS1 it was expected that ANFNS1 encodes a sequence with high identity with the flavanone 2-hydroxylase encoded by licorice CYP93B1, and it was assumed that it encoded a P450 with a function similar to that of flavanone 2-hydroxylase.

However, a comparison with the amino acid sequence of flavanone 2-hydroxylase encoded by CYP93B1 suggested that the cDNA of ANFNS1 is not a full-length cDNA, lacking the portion corresponding to approximately 65 amino acid residues from the initiating methionine. The ANFNS1 CDNA was therefore used as a probe for-rescreening of the snapdragon CDNA library, to obtain CDNA (ANFNS2) which was believed to include the full-length amino acid sequence. The protein encoded by ANFNS2 obtained here exhibited 53% identity on the amino acid level with flavanone 2-hydroxylase encoded by snapdragon-CYP93B1. The nucleotide sequence of ANFNS2 is listed as SEQ.ID. No.1, and the amino acid sequence deduced therefrom is listed as SEQ.ID. No.2.

Example 2 Cloning of Torenia Flavone Synthase II Gene

RNA was extracted from approximately 2 g of buds of a torenia variety (variety name: Sunrenive, variety Registration Application No.: 7433 according to the Seeds and Seedlings Law, by Suntory Ltd.) and the polyA+ RNA was obtained with an oligotex. The polyA+ RNA was used as a template to prepare a cDNA library using a Lambda ZAPII cDNA Library Synthesis Kit (Stratagene) by the method recommended by Stratagene as mentioned in Example 1. The CDNA library was screened using a mixture of the aforementioned CYP93B1 CDNA and ANFNS1 cDNA as the probes. The screening and detection of positive clones were carried out under the low stringent conditions as described in Example 1.

One positive clone was obtained, and was designated as TFNS5. Upon determining the full nucleotide sequence of TFNS5 cDNA, it was found that the protein encoded by TFNS5 cDNA exhibited 52% identity on the amino acid level with flavanone-2-hydroxylase encoded by snapdragon CYP93B1. This TFNS5 cDNA also had high identity of 77% with the protein encoded by ANFNS2, the snapdragon-derived cDNA obtained in Example 1. The determined nucleotide sequence is listed as SEQ.ID. No.3, and the amino acid sequence deduced therefrom is listed as SEQ.ID. No.4.

Example 3 Expression of Torenia Flavone Synthase II Gene in Yeast

The following experiment was conducted in order to detect the enzyme activity of the protein encoded by TFNS5, the torenia cDNA obtained in Example 2. Parts of the outside of the translated region of the gene were modified to introduce restriction enzyme sites therein to prepare a sense primer (5′-AAATAGGATCCAAGCatgGACACAGTCTTAA-3′; underline=BamHI site; lowercase letters: initiation codon) (SEQ.ID. No.5) and an antisense primer (5′-CCCTTCTAGAtcaAGCACCCGATATTGTGGCCGGG-3′; underline=XbaI site; lowercase letters: termination codon) (SEQ.ID. No.6) were used with KOD polymerase (Toyobo) for PCR reaction. The PCR conditions were 98° C. for one minute, 20 cycles of (98° C. for 15 seconds, 55° C. for 10 seconds, 74° C. for 30 seconds), followed by 74° C. for 10 minutes.

After introducing the resultant PCR product into the EcoRV site of pBluescriptII SK(−) (Stratagene), it was digested with restriction enzymes BamHI and XbaI and introduced at the BamHI-XbaI sites of the yeast expression vector pYES2 (Invitrogen). The resultant plasmid was then introduced into BJ2168 yeast (Nihon Gene). The enzyme activity was measured by the method described by Akashi et al. (FEBS Lett., 431 (1998), Akashi et al., p.287). The transformed yeast cells were cultured in 20 ml of selective medium (6.7 mg/ml amino acid-free yeast nitrogen base (Difco), 20 mg/ml glucose, 30 μg/ml leucine, 20 μg/ml tryptophan and 5 mg/ml casamino acid.), at 30° C. for 24 hours.

After harvesting the yeast cells with centrifugation, the harvested yeast cells were cultured at 30° C. for 48 hours in an expressing medium (10 mg/ml yeast extract, 10 mg/ml peptone, 2 μg/ml hemin, 20 mg/ml galactose). After collecting the yeast cells, they were washed by suspending in water and collecting them. Glass beads were used for 10 minutes of disrupting, after which the cells were centrifuged at 8000×g for 10 minutes. The supernatant was further centrifuged at 15,000×g for 10 minutes to obtain a crude enzyme fraction.

A mixture of 15 μg of (R,S)-naringenin (dissolved in 30 μl of 2-methoxyethanol), 1 ml of crude enzyme solution and 1 mM NADPH (total reaction mixture volume: 1.05 ml) was reacted at 30° C. for 2 hours. After terminating the reaction by addition of 30 μl of acetic acid, 1 ml of ethyl acetate was added and mixed therewith. After centrifugation, the ethyl acetate layer was dried with an evaporator. The residue was dissolved in 100 μl of methanol and analyzed by HPLC. The analysis was carried out according to the method described by Akashi et al. The acid treatment involved dissolution of the evaporator-dried sample in 150 μl of ethanol containing 10% hydrochloric acid, and stirring for 30 minutes. This was diluted with 1.3 ml of water, 800 μl of ethyl acetate was further added and mixed therewith, and after centrifugation, the ethyl acetate layer was recovered. This was then dried, dissolved in 200 μl of methanol, and analyzed by HPLC.

The yeast expressing licorice CYP93B1 produced 2-hydroxynaringenin from naringenin, but yielded no apigenin (FIG. 1, A). Only upon acid treatment of the reaction mixture, apigenin was yielded from 2-hydroxynaringenin (FIG. 1, B). In contrast, the yeast expressing torenia TFNS5 yielded apigenin from naringenin without acid treatment of the reaction mixture (FIG. 1, C). This demonstrated that TFNS5 encodes a flavone synthase II.

Example 4 Expression of Snapdragon Flavone Synthase II Gene in Yeast

An approximately 1400 bp DNA fragment obtained by digesting ANFNS2 cDNA with BamHI and SphI, an approximately 350 bp DNA fragment obtained by digesting the same with SphI and BamHI, and pYES2 digested with BamHI and XhoI were ligated to obtain a plasmid, which was then introduced into yeast by the same method as described in Example 3. The resultant recombinant yeast cells were used to measure the flavone synthesis activity by the same method as in Example 3. The yeast expressing the snapdragon-derived ANFNS2 produced apigenin without acid treatment, thus demonstrating that ANFNS2 encodes a flavone synthase II.

Example 5 Construction of Expression Vector in Plants

A plant expression vector was constructed to introduce TFNS5, the torenia cDNA obtained in Example 2, into plants. After digesting pBE2113-GUS (Plant Cell Physiol., 37 (1996), Mitsuhara et al., p.49) with SacI, a blunting kit (Takara) was used to blunt the ends, after which a XhoI linker (Toyobo) was inserted. The resulting plasmid was then digested with HindIII and EcoRI, and an approximately 3 kb DNA fragment was recovered. The DNA fragment was linked to the Hindiii/EcoRI site of the binary vector pBINPLUS to prepare pBE2113′. Vector pBINPLUS used here was obtained by modifying the binary vector Bin19 (Nucl. Acids Res., 12 (1984), Bevan, p.8711), which is widely used for gene introduction into plants using Agrobacterium cells, in the manner reported by van Engelen et al. (Transgenic Research, 4 (1995), van Engelen et al., p.288).

The TFNS5 cDNA was cut out of SK(−) vector by cleavage with BamHI/XhoI, and an approximately 1.7 kb fragment thus obtained was ligated to the BamHI/XhoI sites of the aforementioned binary vector pBE2113′. The construct thus obtained, pSPB441, expresses TFNS5 cDNA in the sense direction under the control of 35S cauliflower mosaic virus promoter having a double repeat of the enhancer sequence (Plant cell Physiol., 37 (1996), Mitsuhara et al., p.49).

Example 6 Alteration of Torenia Flower Color

A torenia variety (variety name: Sunrenive, Variety Registration Application No.: 7433 according to the Seeds and Seedlings Law, by Suntory Ltd.) was transformed with pSPB441 constructed in Example 5 above, according to the method of Aida et al. (Breeding Science, 45 (-1995), Aida et al., p.71). Over 95% of the obtained transformants showed alteration of the flower color from the dark purple of the parent strain to a light purple. The left and the right flower petal colors of four flower petals were measured. While the flower petal color of the parent strain was Number 89A according to the Royal Horticultural Society Color Chart, the typical flower petal colors of the transformants were 82C, 87D, 87C, 88D, 91A, etc. These results indicated that introduction of TFNS5 into plants can alter flower colors.

In the transformed individuals, the amount of flavones ranged ⅕ to {fraction (1/10)} that of the host, while the amount of anthocyanins was reduced to about ⅓ that of the host. Also detected were flavanones (naringenin, eriodictyol and pentahydroxyflavanone) which are flavone biosynthesis precursors that were not detected in the host.

Example 7 Expression of Flavone Synthase in Petunias

Plasmid pSPB441 was introduced into a petunia variety (variety name: Revolution Violet Mini, Variety Registration Application No.: 9217, according to the Seeds and Seedlings Law, by Suntory Ltd.) according to the method of Napoli et al. (Plant Cell, 2, (1990), Napoli et al., p.279). Changes in flower colors occurred in two of the resultant transformants, where the flower colors were lighter than the parent strain. The flower color of the parent strain was Number 88A according to the Royal Horticultural Society Color Chart, whereas 87A in the transformants. Also, while no flavones were detected in the parent strain, a flavone, luteolin, was detected in the transformed strains.

Example 8 Cloning of Perilla Flavone Synthase II Gene

The method described in Example 1 was used to screen a cDNA library prepared-from leaves of red perilla (Perilla frutescens) according to the method of Gong et al. (Plant Mol. Biol., 35, (1997), Gong et al., p.915) using λgt10 (Stratagene) as the vector. Culturing, DNA preparation and subcloning of the resulting phage clones #3 were carried out according to the method of Gong et al. (Plant Mol. Biol., 35, (1997), Gong et al., p.915), and the nucleotide sequence was determined and listed as SEQ.ID. No.7. The deduced amino acid sequence encoded by this nucleotide sequence was listed as SEQ.ID. No.8. This amino acid sequence showed 76% and 75% identity with TFNS5 and ANFNS2, respectively. It also showed 52% identity with CYP93B1.

Example 9 Expression of Nerilla Flavone Synthase II Gene in Yeast

The phage clone #3 obtained in Example 8 was used as a template for PCR by the method described in Example 3, using Lambda Arm Primer (Stratagene). The amplified DNA fragment was subcloned at the EcoRV site of pBluescript KS(−). A clone with the initiation codon of perilla flavone synthase II cDNA on the SalI site side of pBluescript KS(−) was selected, and was designated as pFS3. The nucleotide sequence of the cDNA insert of pFS3 was determined, and PCR was conducted to confirm the absence of errors.

An approximately 1.8 kb DNA fragment obtained by digesting pFS3 with SalI and XbaI was ligated with pYES2 digested with XhoI and XbaI (Example 3) to obtain a plasmid which was designated as pYFS3, and this was introduced into yeast BJ2168 by the method described in Example 3. When the flavone synthase activity of this recombinant yeast was measured by the method described in Example 3, production of apigenin from naringenin was confirmed, indicating that the perilla phage clone #3 cDNA encodes a protein with flavone synthase II activity.

INDUSTRIAL APPLICABILITY

It is possible to alter flower colors by linking cDNA of the invention to an appropriate plant expression vector and introducing it into plants to express or inhibit expression of flavone synthases. Furthermore, by expressing the flavone synthase genes not only in petals but also in entire plants or their appropriate organs, it is possible to increase the resistance against microorganisms of plants or to improve the nitrogen fixing ability of legumes by promoting association with rhizosphere microorganisms, as well as to improve the protective effects of plants against ultraviolet rays and light.

8 1 1724 DNA Antirrhinum majus Nucleotide sequence encoding a protein having an activity to directly convert flavanone to flavone 1 gctttacaca cacacacaca cacacacaca caaacaaaa atg tct aca ctt gtc 54 Met Ser Thr Leu Val 1 5 tac agc aca ctc ttc atc ctc tca acc ctc ctc ctc acc ctc cta acc 102 Tyr Ser Thr Leu Phe Ile Leu Ser Thr Leu Leu Leu Thr Leu Leu Thr 10 15 20 cgc acc cgc cgc aag acc cgc ccg ccc ggc cca tta gcc ctc ccc tta 150 Arg Thr Arg Arg Lys Thr Arg Pro Pro Gly Pro Leu Ala Leu Pro Leu 25 30 35 ata ggc cac tta cac ctc ctc ggc cca aag ctc cac cac acc ttc cac 198 Ile Gly His Leu His Leu Leu Gly Pro Lys Leu His His Thr Phe His 40 45 50 caa ttc tcc caa cgc tac ggc ccg ctc atc cag ctc tac ctc ggc tcc 246 Gln Phe Ser Gln Arg Tyr Gly Pro Leu Ile Gln Leu Tyr Leu Gly Ser 55 60 65 gtc cca tgc gtc gtc gct tcc acg ccc gaa ctc gcc cgc gaa ttc ctc 294 Val Pro Cys Val Val Ala Ser Thr Pro Glu Leu Ala Arg Glu Phe Leu 70 75 80 85 aag acg cac gaa ctc gac ttc tcg tcc cgc aag cac tcc acc gcc atc 342 Lys Thr His Glu Leu Asp Phe Ser Ser Arg Lys His Ser Thr Ala Ile 90 95 100 gac atc gtc acg tac gac tcc tcg ttc gcc ttc gcg ccg tac ggg ccg 390 Asp Ile Val Thr Tyr Asp Ser Ser Phe Ala Phe Ala Pro Tyr Gly Pro 105 110 115 tac tgg aaa ttc atc aag aaa tta tgt act tac gag cta ctg ggt gcc 438 Tyr Trp Lys Phe Ile Lys Lys Leu Cys Thr Tyr Glu Leu Leu Gly Ala 120 125 130 cgg aac ttg agc cat ttc cag ccc att aga gct ttg gag gtc aac agt 486 Arg Asn Leu Ser His Phe Gln Pro Ile Arg Ala Leu Glu Val Asn Ser 135 140 145 ttc ttg aga att ttg tac gag aaa aca gag cag aaa cag agt gtt aat 534 Phe Leu Arg Ile Leu Tyr Glu Lys Thr Glu Gln Lys Gln Ser Val Asn 150 155 160 165 gtg act gag gag ctt gtg aag ctg acg agt aat gtg atc agt aac atg 582 Val Thr Glu Glu Leu Val Lys Leu Thr Ser Asn Val Ile Ser Asn Met 170 175 180 atg ttg ggg atc agg tgt tcg ggg acg gaa ggg gag gcg gag gtg gcg 630 Met Leu Gly Ile Arg Cys Ser Gly Thr Glu Gly Glu Ala Glu Val Ala 185 190 195 agg acg gtg ata agg gag gtg acg cag ata ttt ggg gag ttt gat gtg 678 Arg Thr Val Ile Arg Glu Val Thr Gln Ile Phe Gly Glu Phe Asp Val 200 205 210 tcg gag att gtt tgg ttt tgt aag aat ttg gat ctg cag ggg att agg 726 Ser Glu Ile Val Trp Phe Cys Lys Asn Leu Asp Leu Gln Gly Ile Arg 215 220 225 aag agg tcg gag gat att agg agg agg tat gat gct ttg ttg gag aag 774 Lys Arg Ser Glu Asp Ile Arg Arg Arg Tyr Asp Ala Leu Leu Glu Lys 230 235 240 245 att att agt gat agg gag agg ttg agg ttg agg ggg ggt ggt ggt gga 822 Ile Ile Ser Asp Arg Glu Arg Leu Arg Leu Arg Gly Gly Gly Gly Gly 250 255 260 ggg ggt gga gag gtg aag gat ttt ttg gat atg ttg ttg gat gtg atg 870 Gly Gly Gly Glu Val Lys Asp Phe Leu Asp Met Leu Leu Asp Val Met 265 270 275 gag agt gag aaa tcg gag gtg gag ttt acg agg gag cat ctc aaa gct 918 Glu Ser Glu Lys Ser Glu Val Glu Phe Thr Arg Glu His Leu Lys Ala 280 285 290 ttg att ctg gat ttc ttc act gcc ggt aca gac aca aca gca atc aca 966 Leu Ile Leu Asp Phe Phe Thr Ala Gly Thr Asp Thr Thr Ala Ile Thr 295 300 305 aca gaa tgg gca ata gca gaa ctc att agc aat cca aat gta ctc aaa 1014 Thr Glu Trp Ala Ile Ala Glu Leu Ile Ser Asn Pro Asn Val Leu Lys 310 315 320 325 aaa gct caa gaa gag atg gac aaa gtc ata gga tca caa agg ttg ttg 1062 Lys Ala Gln Glu Glu Met Asp Lys Val Ile Gly Ser Gln Arg Leu Leu 330 335 340 caa gaa tcc gac gcc cct aac ttg cct tac ctc aac gcg atc ata aaa 1110 Gln Glu Ser Asp Ala Pro Asn Leu Pro Tyr Leu Asn Ala Ile Ile Lys 345 350 355 gaa acg ttc cgt ctc cac cct cca atc ccc atg ctc act aga aaa tca 1158 Glu Thr Phe Arg Leu His Pro Pro Ile Pro Met Leu Thr Arg Lys Ser 360 365 370 att tct gac gtt gtg gtc aac ggg tac acg atc cct gcc aaa acg cta 1206 Ile Ser Asp Val Val Val Asn Gly Tyr Thr Ile Pro Ala Lys Thr Leu 375 380 385 ttg ttt gtc aac ctt tgg tcc atg gga agg aat cct aac tac tgg gaa 1254 Leu Phe Val Asn Leu Trp Ser Met Gly Arg Asn Pro Asn Tyr Trp Glu 390 395 400 405 aat ccg atg gag ttc cga ccc gag agg ttt ctc gag aaa ggg acc ggg 1302 Asn Pro Met Glu Phe Arg Pro Glu Arg Phe Leu Glu Lys Gly Thr Gly 410 415 420 tcg ata gac gtt aaa ggg cag cat ttc gag ttg ctg ccg ttt ggc acg 1350 Ser Ile Asp Val Lys Gly Gln His Phe Glu Leu Leu Pro Phe Gly Thr 425 430 435 ggc agg cgg ggc tgc ccg ggg atg ttg tta ggc atg cag gag ttg ttt 1398 Gly Arg Arg Gly Cys Pro Gly Met Leu Leu Gly Met Gln Glu Leu Phe 440 445 450 agt att atc ggg gct atg gtg cag tgc ttc gat tgg aaa ctg ccc gat 1446 Ser Ile Ile Gly Ala Met Val Gln Cys Phe Asp Trp Lys Leu Pro Asp 455 460 465 ggt gtg aag tcg gtc gac atg acc gag cgg ccc ggg ttg acg gct cca 1494 Gly Val Lys Ser Val Asp Met Thr Glu Arg Pro Gly Leu Thr Ala Pro 470 475 480 485 cgt gcc aat gat ttg gtg tgc caa ttg gtg cca cgg att gac ccg gtc 1542 Arg Ala Asn Asp Leu Val Cys Gln Leu Val Pro Arg Ile Asp Pro Val 490 495 500 gtt gtc tcc gga ccg tgaaccttaa ggtagtatcg ataatctgtt taatt 1592 Val Val Ser Gly Pro 505 aaattgttat ttgttgtgag gatttgattt ttgttatgta tgattatgcg tggattaaga 1652 taagcctgca aggacaaatt ccctttcttt gattgatgtc aatgagtttg tgtcaaaaaa 1712 aaaaaaaaaa aa 1724 2 506 PRT Antirrhinum majus Amino acid sequence of a protein having an activity to directly convert flavanone to flavone 2 Met Ser Thr Leu Val Tyr Ser Thr Leu Phe Ile Leu Ser Thr Leu Leu 1 5 10 15 Leu Thr Leu Leu Thr Arg Thr Arg Arg Lys Thr Arg Pro Pro Gly Pro 20 25 30 Leu Ala Leu Pro Leu Ile Gly His Leu His Leu Leu Gly Pro Lys Leu 35 40 45 His His Thr Phe His Gln Phe Ser Gln Arg Tyr Gly Pro Leu Ile Gln 50 55 60 Leu Tyr Leu Gly Ser Val Pro Cys Val Val Ala Ser Thr Pro Glu Leu 65 70 75 80 Ala Arg Glu Phe Leu Lys Thr His Glu Leu Asp Phe Ser Ser Arg Lys 85 90 95 His Ser Thr Ala Ile Asp Ile Val Thr Tyr Asp Ser Ser Phe Ala Phe 100 105 110 Ala Pro Tyr Gly Pro Tyr Trp Lys Phe Ile Lys Lys Leu Cys Thr Tyr 115 120 125 Glu Leu Leu Gly Ala Arg Asn Leu Ser His Phe Gln Pro Ile Arg Ala 130 135 140 Leu Glu Val Asn Ser Phe Leu Arg Ile Leu Tyr Glu Lys Thr Glu Gln 145 150 155 160 Lys Gln Ser Val Asn Val Thr Glu Glu Leu Val Lys Leu Thr Ser Asn 165 170 175 Val Ile Ser Asn Met Met Leu Gly Ile Arg Cys Ser Gly Thr Glu Gly 180 185 190 Glu Ala Glu Val Ala Arg Thr Val Ile Arg Glu Val Thr Gln Ile Phe 195 200 205 Gly Glu Phe Asp Val Ser Glu Ile Val Trp Phe Cys Lys Asn Leu Asp 210 215 220 Leu Gln Gly Ile Arg Lys Arg Ser Glu Asp Ile Arg Arg Arg Tyr Asp 225 230 235 240 Ala Leu Leu Glu Lys Ile Ile Ser Asp Arg Glu Arg Leu Arg Leu Arg 245 250 255 Gly Gly Gly Gly Gly Gly Gly Gly Glu Val Lys Asp Phe Leu Asp Met 260 265 270 Leu Leu Asp Val Met Glu Ser Glu Lys Ser Glu Val Glu Phe Thr Arg 275 280 285 Glu His Leu Lys Ala Leu Ile Leu Asp Phe Phe Thr Ala Gly Thr Asp 290 295 300 Thr Thr Ala Ile Thr Thr Glu Trp Ala Ile Ala Glu Leu Ile Ser Asn 305 310 315 320 Pro Asn Val Leu Lys Lys Ala Gln Glu Glu Met Asp Lys Val Ile Gly 325 330 335 Ser Gln Arg Leu Leu Gln Glu Ser Asp Ala Pro Asn Leu Pro Tyr Leu 340 345 350 Asn Ala Ile Ile Lys Glu Thr Phe Arg Leu His Pro Pro Ile Pro Met 355 360 365 Leu Thr Arg Lys Ser Ile Ser Asp Val Val Val Asn Gly Tyr Thr Ile 370 375 380 Pro Ala Lys Thr Leu Leu Phe Val Asn Leu Trp Ser Met Gly Arg Asn 385 390 395 400 Pro Asn Tyr Trp Glu Asn Pro Met Glu Phe Arg Pro Glu Arg Phe Leu 405 410 415 Glu Lys Gly Thr Gly Ser Ile Asp Val Lys Gly Gln His Phe Glu Leu 420 425 430 Leu Pro Phe Gly Thr Gly Arg Arg Gly Cys Pro Gly Met Leu Leu Gly 435 440 445 Met Gln Glu Leu Phe Ser Ile Ile Gly Ala Met Val Gln Cys Phe Asp 450 455 460 Trp Lys Leu Pro Asp Gly Val Lys Ser Val Asp Met Thr Glu Arg Pro 465 470 475 480 Gly Leu Thr Ala Pro Arg Ala Asn Asp Leu Val Cys Gln Leu Val Pro 485 490 495 Arg Ile Asp Pro Val Val Val Ser Gly Pro 500 505 3 1730 DNA Torenia hybrida Nucleotide sequence encoding a protein having an activity to directly convert flavanone to flavone 3 atcgaaaccg ctatatcatt acatttacaa cagcgctaaa aaaatatata taaagc 56 atg gac aca gtc tta atc aca ctc tac acc gcc ctg ttc gtc atc acc 104 Met Asp Thr Val Leu Ile Thr Leu Tyr Thr Ala Leu Phe Val Ile Thr 1 5 10 15 acc acc ttc ctc ctc ctc ctc cgc cga agg gga cca ccg tct ccg ccc 152 Thr Thr Phe Leu Leu Leu Leu Arg Arg Arg Gly Pro Pro Ser Pro Pro 20 25 30 ggt cct ctc tcc cta ccc ata att ggc cac ctc cac ctc ctc ggc cca 200 Gly Pro Leu Ser Leu Pro Ile Ile Gly His Leu His Leu Leu Gly Pro 35 40 45 aga ctc cac cac acg ttc cat gaa ttc tca ctc aaa tac ggc cca ttg 248 Arg Leu His His Thr Phe His Glu Phe Ser Leu Lys Tyr Gly Pro Leu 50 55 60 atc cag ctc aag ctc ggc tcg atc ccg tgc gtc gtg gcc tcg acg ccc 296 Ile Gln Leu Lys Leu Gly Ser Ile Pro Cys Val Val Ala Ser Thr Pro 65 70 75 80 gag ctc gcg aga gag ttt ctt aag acg aac gag ctc gcg ttc tcc tct 344 Glu Leu Ala Arg Glu Phe Leu Lys Thr Asn Glu Leu Ala Phe Ser Ser 85 90 95 cgc aag cac tct acg gcc ata gac atc gtc acc tac gac tcg tcc ttt 392 Arg Lys His Ser Thr Ala Ile Asp Ile Val Thr Tyr Asp Ser Ser Phe 100 105 110 gct ttc tct ccg tac gga ccc tac tgg aag tac atc aag aaa ctg tgt 440 Ala Phe Ser Pro Tyr Gly Pro Tyr Trp Lys Tyr Ile Lys Lys Leu Cys 115 120 125 acc tac gag ctg ctc gga gcg agg aac ctc gga cac ttt cag ccc att 488 Thr Tyr Glu Leu Leu Gly Ala Arg Asn Leu Gly His Phe Gln Pro Ile 130 135 140 agg aat ctc gag gtc agg tcc ttt ctg cag ctt ctg atg cac aag agc 536 Arg Asn Leu Glu Val Arg Ser Phe Leu Gln Leu Leu Met His Lys Ser 145 150 155 160 ttt aag ggc gag agt gtg aat gtg aca gac gag ctg gtg agg ctg acg 584 Phe Lys Gly Glu Ser Val Asn Val Thr Asp Glu Leu Val Arg Leu Thr 165 170 175 agc aat gtg ata tcc cac atg atg ctg agc ata agg tgc tcg gaa gat 632 Ser Asn Val Ile Ser His Met Met Leu Ser Ile Arg Cys Ser Glu Asp 180 185 190 gaa ggc gat gct gag gcg gcg aga aca gtg ata cgc gag gtg acg cag 680 Glu Gly Asp Ala Glu Ala Ala Arg Thr Val Ile Arg Glu Val Thr Gln 195 200 205 ata ttt ggg gaa ttc gat gtt acg gac ata ata tgg ttt tgc aag aaa 728 Ile Phe Gly Glu Phe Asp Val Thr Asp Ile Ile Trp Phe Cys Lys Lys 210 215 220 ttc gat ctg cag ggg ata aag aag agg tca gag gat att cag agg agg 776 Phe Asp Leu Gln Gly Ile Lys Lys Arg Ser Glu Asp Ile Gln Arg Arg 225 230 235 240 tat gat gct ttg ctc gag aag att att agt gat aga gag aga tcg agg 824 Tyr Asp Ala Leu Leu Glu Lys Ile Ile Ser Asp Arg Glu Arg Ser Arg 245 250 255 agg caa aat cgt gat aag cat ggt ggc ggt aac aat gag gag gcc aag 872 Arg Gln Asn Arg Asp Lys His Gly Gly Gly Asn Asn Glu Glu Ala Lys 260 265 270 gat ttt ctt gat atg ttg ctt gat gtg atg gag agt ggg gac acg gag 920 Asp Phe Leu Asp Met Leu Leu Asp Val Met Glu Ser Gly Asp Thr Glu 275 280 285 gtc aaa ttc act aga gag cat ctc aag gct ttg att ctg gat ttc ttc 968 Val Lys Phe Thr Arg Glu His Leu Lys Ala Leu Ile Leu Asp Phe Phe 290 295 300 acg gcc ggt acg gac aca aca gcc ata gcc acc gag tgg gcc atc gcc 1016 Thr Ala Gly Thr Asp Thr Thr Ala Ile Ala Thr Glu Trp Ala Ile Ala 305 310 315 320 gag ctc atc aac aac ccg aac gtc ttg aag aag gcc caa gaa gaa ata 1064 Glu Leu Ile Asn Asn Pro Asn Val Leu Lys Lys Ala Gln Glu Glu Ile 325 330 335 tcc cgg atc atc gga acc aag cgg atc gta caa gaa tcc gac gcc cca 1112 Ser Arg Ile Ile Gly Thr Lys Arg Ile Val Gln Glu Ser Asp Ala Pro 340 345 350 gac cta ccc tac ctc cag gcc atc atc aag gag acg ttc cgg ctc cac 1160 Asp Leu Pro Tyr Leu Gln Ala Ile Ile Lys Glu Thr Phe Arg Leu His 355 360 365 cca ccg atc ccg atg ctc tcg cgt aag tcc acc tcc gat tgc acg gtc 1208 Pro Pro Ile Pro Met Leu Ser Arg Lys Ser Thr Ser Asp Cys Thr Val 370 375 380 aac ggc tac aaa atc caa gcc aag agc ctc ttg ttc gtg aac ata tgg 1256 Asn Gly Tyr Lys Ile Gln Ala Lys Ser Leu Leu Phe Val Asn Ile Trp 385 390 395 400 tcc atc ggt cga aac cct aat tac tgg gaa agc cct atg gag ttc agg 1304 Ser Ile Gly Arg Asn Pro Asn Tyr Trp Glu Ser Pro Met Glu Phe Arg 405 410 415 ccc gag cgg ttc ttg gag aag gga cgc gag tcc atc gac gtc aag ggc 1352 Pro Glu Arg Phe Leu Glu Lys Gly Arg Glu Ser Ile Asp Val Lys Gly 420 425 430 cag cac ttt gag ctc ttg cct ttt ggg acg ggc cgc agg ggc tgt ccc 1400 Gln His Phe Glu Leu Leu Pro Phe Gly Thr Gly Arg Arg Gly Cys Pro 435 440 445 ggt atg ttg ctg gct ata caa gag gtg gtc agc atc att ggg acc atg 1448 Gly Met Leu Leu Ala Ile Gln Glu Val Val Ser Ile Ile Gly Thr Met 450 455 460 gtt cag tgc ttc gac tgg aaa ttg gca gat ggt tcg ggc aat aat gtg 1496 Val Gln Cys Phe Asp Trp Lys Leu Ala Asp Gly Ser Gly Asn Asn Val 465 470 475 480 gac atg acc gaa cgg tct gga ttg acc gct ccg aga gcg ttc gat ctg 1544 Asp Met Thr Glu Arg Ser Gly Leu Thr Ala Pro Arg Ala Phe Asp Leu 485 490 495 gtt tgc cgg ttg tat cca cgg gtt gac ccg gcc aca ata tcg ggt gct 1592 Val Cys Arg Leu Tyr Pro Arg Val Asp Pro Ala Thr Ile Ser Gly Ala 500 505 510 512 tgatgtagta gggtgaggcg cgtgttggtg ttttatcttt cggttttgtt ctgttagtat 1652 tattatggtc tgtgttgaag cctcaaggat tttaaaaaaa aaaaaaaaaa aaaaaaaaaa 1712 aaaaaaaaaa aaaaaaaa 1730 4 512 PRT Torenia hybrida Amino acid sequence of a protein having an activity to directly convert flavanone to flavone 4 Met Asp Thr Val Leu Ile Thr Leu Tyr Thr Ala Leu Phe Val Ile Thr 1 5 10 15 Thr Thr Phe Leu Leu Leu Leu Arg Arg Arg Gly Pro Pro Ser Pro Pro 20 25 30 Gly Pro Leu Ser Leu Pro Ile Ile Gly His Leu His Leu Leu Gly Pro 35 40 45 Arg Leu His His Thr Phe His Glu Phe Ser Leu Lys Tyr Gly Pro Leu 50 55 60 Ile Gln Leu Lys Leu Gly Ser Ile Pro Cys Val Val Ala Ser Thr Pro 65 70 75 80 Glu Leu Ala Arg Glu Phe Leu Lys Thr Asn Glu Leu Ala Phe Ser Ser 85 90 95 Arg Lys His Ser Thr Ala Ile Asp Ile Val Thr Tyr Asp Ser Ser Phe 100 105 110 Ala Phe Ser Pro Tyr Gly Pro Tyr Trp Lys Tyr Ile Lys Lys Leu Cys 115 120 125 Thr Tyr Glu Leu Leu Gly Ala Arg Asn Leu Gly His Phe Gln Pro Ile 130 135 140 Arg Asn Leu Glu Val Arg Ser Phe Leu Gln Leu Leu Met His Lys Ser 145 150 155 160 Phe Lys Gly Glu Ser Val Asn Val Thr Asp Glu Leu Val Arg Leu Thr 165 170 175 Ser Asn Val Ile Ser His Met Met Leu Ser Ile Arg Cys Ser Glu Asp 180 185 190 Glu Gly Asp Ala Glu Ala Ala Arg Thr Val Ile Arg Glu Val Thr Gln 195 200 205 Ile Phe Gly Glu Phe Asp Val Thr Asp Ile Ile Trp Phe Cys Lys Lys 210 215 220 Phe Asp Leu Gln Gly Ile Lys Lys Arg Ser Glu Asp Ile Gln Arg Arg 225 230 235 240 Tyr Asp Ala Leu Leu Glu Lys Ile Ile Ser Asp Arg Glu Arg Ser Arg 245 250 255 Arg Gln Asn Arg Asp Lys His Gly Gly Gly Asn Asn Glu Glu Ala Lys 260 265 270 Asp Phe Leu Asp Met Leu Leu Asp Val Met Glu Ser Gly Asp Thr Glu 275 280 285 Val Lys Phe Thr Arg Glu His Leu Lys Ala Leu Ile Leu Asp Phe Phe 290 295 300 Thr Ala Gly Thr Asp Thr Thr Ala Ile Ala Thr Glu Trp Ala Ile Ala 305 310 315 320 Glu Leu Ile Asn Asn Pro Asn Val Leu Lys Lys Ala Gln Glu Glu Ile 325 330 335 Ser Arg Ile Ile Gly Thr Lys Arg Ile Val Gln Glu Ser Asp Ala Pro 340 345 350 Asp Leu Pro Tyr Leu Gln Ala Ile Ile Lys Glu Thr Phe Arg Leu His 355 360 365 Pro Pro Ile Pro Met Leu Ser Arg Lys Ser Thr Ser Asp Cys Thr Val 370 375 380 Asn Gly Tyr Lys Ile Gln Ala Lys Ser Leu Leu Phe Val Asn Ile Trp 385 390 395 400 Ser Ile Gly Arg Asn Pro Asn Tyr Trp Glu Ser Pro Met Glu Phe Arg 405 410 415 Pro Glu Arg Phe Leu Glu Lys Gly Arg Glu Ser Ile Asp Val Lys Gly 420 425 430 Gln His Phe Glu Leu Leu Pro Phe Gly Thr Gly Arg Arg Gly Cys Pro 435 440 445 Gly Met Leu Leu Ala Ile Gln Glu Val Val Ser Ile Ile Gly Thr Met 450 455 460 Val Gln Cys Phe Asp Trp Lys Leu Ala Asp Gly Ser Gly Asn Asn Val 465 470 475 480 Asp Met Thr Glu Arg Ser Gly Leu Thr Ala Pro Arg Ala Phe Asp Leu 485 490 495 Val Cys Arg Leu Tyr Pro Arg Val Asp Pro Ala Thr Ile Ser Gly Ala 500 505 510 5 31 DNA Artificial Sequence Primer 5 aaataggatc caagcatgga cacagtctta a 31 6 35 DNA Artificial Sequence Primer 6 cccttctaga tcaagcaccc gatattgtgg ccggg 35 7 1770 DNA Perilla frutescens Nucleotide sequence encoding a protein having an activity to directly convert flavanone to flavone 7 tgtcgacgga gcaagtggaa atg gca ctg tac gcc gcc ctc ttc ctc ctg tcc 53 Met Ala Leu Tyr Ala Ala Leu Phe Leu Leu Ser 1 5 10 gcc gcc gtg gtc cgc tcc gtt ctg gat cga aaa cgc ggg cgg ccg ccc 101 Ala Ala Val Val Arg Ser Val Leu Asp Arg Lys Arg Gly Arg Pro Pro 15 20 25 tac cct ccc ggg ccg ttc cct ctt ccc atc atc ggc cac tta cac ctc 149 Tyr Pro Pro Gly Pro Phe Pro Leu Pro Ile Ile Gly His Leu His Leu 30 35 40 ctc ggg ccg aga ctc cac caa acc ttc cac gat ctg tcc caa cgg tac 197 Leu Gly Pro Arg Leu His Gln Thr Phe His Asp Leu Ser Gln Arg Tyr 45 50 55 ggg ccc tta atg cag ctc cgc ctc ggg tcc atc cgc tgc gtc att gct 245 Gly Pro Leu Met Gln Leu Arg Leu Gly Ser Ile Arg Cys Val Ile Ala 60 65 70 75 gcc tcg ccg gag ctc gcc aag gaa tgc ctc aag aca cac gag ctc gtc 293 Ala Ser Pro Glu Leu Ala Lys Glu Cys Leu Lys Thr His Glu Leu Val 80 85 90 ttc tcc tcc cgc aaa cac tcc acc gcc att gat atc gtc acc tac gat 341 Phe Ser Ser Arg Lys His Ser Thr Ala Ile Asp Ile Val Thr Tyr Asp 95 100 105 tca tcc ttc gct ttc tct ccc tac ggg cct tac tgg aaa ttc atc aag 389 Ser Ser Phe Ala Phe Ser Pro Tyr Gly Pro Tyr Trp Lys Phe Ile Lys 110 115 120 aaa tta tgc acc tac gag ctg ctc ggg gcc cga aat ctc gcc cac ttt 437 Lys Leu Cys Thr Tyr Glu Leu Leu Gly Ala Arg Asn Leu Ala His Phe 125 130 135 cag ccc atc agg act ctc gaa gtc aag tct ttc ctc caa att ctt atg 485 Gln Pro Ile Arg Thr Leu Glu Val Lys Ser Phe Leu Gln Ile Leu Met 140 145 150 155 cgc aag ggt gaa tcg ggg gag agc ttc aac gtg act gag gag ctc gtg 533 Arg Lys Gly Glu Ser Gly Glu Ser Phe Asn Val Thr Glu Glu Leu Val 160 165 170 aag ctg acg agc aac gtc ata tcg cat atg atg ctg agc ata cgg tgt 581 Lys Leu Thr Ser Asn Val Ile Ser His Met Met Leu Ser Ile Arg Cys 175 180 185 tca gag acg gag tcg gag gcg gag gcg gcg agg acg gtg att cgg gag 629 Ser Glu Thr Glu Ser Glu Ala Glu Ala Ala Arg Thr Val Ile Arg Glu 190 195 200 gtc acg cag ata ttt ggg gag ttc gac gtc tcc gac atc ata tgg ctt 677 Val Thr Gln Ile Phe Gly Glu Phe Asp Val Ser Asp Ile Ile Trp Leu 205 210 215 tgt aag aac ttc gat ttc caa ggt ata agg aag cgg tcc gag gat atc 725 Cys Lys Asn Phe Asp Phe Gln Gly Ile Arg Lys Arg Ser Glu Asp Ile 220 225 230 235 cag agg aga tat gat gct ctg ctg gag aag atc atc acc gac aga gag 773 Gln Arg Arg Tyr Asp Ala Leu Leu Glu Lys Ile Ile Thr Asp Arg Glu 240 245 250 aag cag agg cgg acc cac ggc ggc ggt ggc ggc ggc ggg gaa gcc aag 821 Lys Gln Arg Arg Thr His Gly Gly Gly Gly Gly Gly Gly Glu Ala Lys 255 260 265 gat ttt ctt gac atg ttc ctc gac ata atg gag agc ggg aaa gcc gaa 869 Asp Phe Leu Asp Met Phe Leu Asp Ile Met Glu Ser Gly Lys Ala Glu 270 275 280 gtt aaa ttc acg agg gag cat ctc aaa gct ttg att ctg gat ttc ttc 917 Val Lys Phe Thr Arg Glu His Leu Lys Ala Leu Ile Leu Asp Phe Phe 285 290 295 acc gcc ggc acc gac acg acg gcg atc gtg tgt gaa tgg gcg ata gca 965 Thr Ala Gly Thr Asp Thr Thr Ala Ile Val Cys Glu Trp Ala Ile Ala 300 305 310 315 gaa gtg atc aac aat cca aat gtg ttg aag aaa gct caa gaa gag att 1013 Glu Val Ile Asn Asn Pro Asn Val Leu Lys Lys Ala Gln Glu Glu Ile 320 325 330 gcc aac atc gtc gga ttc gac aga att ctg caa gaa tcc gac gcc cca 1061 Ala Asn Ile Val Gly Phe Asp Arg Ile Leu Gln Glu Ser Asp Ala Pro 335 340 345 aat ctg ccc tac ctt caa gcc ctc atc aaa gaa aca ttc cgg ctc cac 1109 Asn Leu Pro Tyr Leu Gln Ala Leu Ile Lys Glu Thr Phe Arg Leu His 350 355 360 cct cca atc cca atg ctg gcg agg aaa tcg atc tcc gac tgc gtc atc 1157 Pro Pro Ile Pro Met Leu Ala Arg Lys Ser Ile Ser Asp Cys Val Ile 365 370 375 gac ggc tac atg att ccg gcc aac acg ctg ctc ttc gtc aac ctc tgg 1205 Asp Gly Tyr Met Ile Pro Ala Asn Thr Leu Leu Phe Val Asn Leu Trp 380 385 390 395 tcc atg ggg cgg aac cct aaa atc tgg gac tac ccg acg gcg ttc cag 1253 Ser Met Gly Arg Asn Pro Lys Ile Trp Asp Tyr Pro Thr Ala Phe Gln 400 405 410 ccg gag agg ttt ctg gag aag gaa aag gcc gcc atc gat gtt aaa ggg 1301 Pro Glu Arg Phe Leu Glu Lys Glu Lys Ala Ala Ile Asp Val Lys Gly 415 420 425 cag cat ttt gag ctg cta ccg ttc gga acg ggc agg aga ggc tgc cca 1349 Gln His Phe Glu Leu Leu Pro Phe Gly Thr Gly Arg Arg Gly Cys Pro 430 435 440 ggg atg ctt tta gcc att cag gag gtg gtc atc ata att ggg acg atg 1397 Gly Met Leu Leu Ala Ile Gln Glu Val Val Ile Ile Ile Gly Thr Met 445 450 455 att caa tgc ttc gat tgg aag ctg ccc gac ggc tcc ggc cat gtt gat 1445 Ile Gln Cys Phe Asp Trp Lys Leu Pro Asp Gly Ser Gly His Val Asp 460 465 470 475 atg gca gaa cgg cca ggg ctc acg gca ccg cga gag acc gat ttg ttt 1493 Met Ala Glu Arg Pro Gly Leu Thr Ala Pro Arg Glu Thr Asp Leu Phe 480 485 490 tgc cgt gtg gtg ccg cga gtt gat ccg ttg gtt gtt tcc acc cag 1538 Cys Arg Val Val Pro Arg Val Asp Pro Leu Val Val Ser Thr Gln 495 500 505 tgatcacccc ctttaaattt attaatgata tatttttatt ttgagaaaaa ataaaaatgc 1598 taattgtttt gtttcatgat gtaattgtta attagtttct attgtgcgct gtcgcgtgtc 1658 gcgtggctta agataagatt gtatcattgg tacctaggat gtattttcat tttcaataaa 1718 ttattttgtg ctgtgtatat taaaaaaaaa aaagaaaaaa aaaaaaaaaa aa 1770 8 506 PRT Perilla frutescens Amino acid sequence of a protein having an activity to directly convert flavanone to flavone 8 Met Ala Leu Tyr Ala Ala Leu Phe Leu Leu Ser Ala Ala Val Val Arg 1 5 10 15 Ser Val Leu Asp Arg Lys Arg Gly Arg Pro Pro Tyr Pro Pro Gly Pro 20 25 30 Phe Pro Leu Pro Ile Ile Gly His Leu His Leu Leu Gly Pro Arg Leu 35 40 45 His Gln Thr Phe His Asp Leu Ser Gln Arg Tyr Gly Pro Leu Met Gln 50 55 60 Leu Arg Leu Gly Ser Ile Arg Cys Val Ile Ala Ala Ser Pro Glu Leu 65 70 75 80 Ala Lys Glu Cys Leu Lys Thr His Glu Leu Val Phe Ser Ser Arg Lys 85 90 95 His Ser Thr Ala Ile Asp Ile Val Thr Tyr Asp Ser Ser Phe Ala Phe 100 105 110 Ser Pro Tyr Gly Pro Tyr Trp Lys Phe Ile Lys Lys Leu Cys Thr Tyr 115 120 125 Glu Leu Leu Gly Ala Arg Asn Leu Ala His Phe Gln Pro Ile Arg Thr 130 135 140 Leu Glu Val Lys Ser Phe Leu Gln Ile Leu Met Arg Lys Gly Glu Ser 145 150 155 160 Gly Glu Ser Phe Asn Val Thr Glu Glu Leu Val Lys Leu Thr Ser Asn 165 170 175 Val Ile Ser His Met Met Leu Ser Ile Arg Cys Ser Glu Thr Glu Ser 180 185 190 Glu Ala Glu Ala Ala Arg Thr Val Ile Arg Glu Val Thr Gln Ile Phe 195 200 205 Gly Glu Phe Asp Val Ser Asp Ile Ile Trp Leu Cys Lys Asn Phe Asp 210 215 220 Phe Gln Gly Ile Arg Lys Arg Ser Glu Asp Ile Gln Arg Arg Tyr Asp 225 230 235 240 Ala Leu Leu Glu Lys Ile Ile Thr Asp Arg Glu Lys Gln Arg Arg Thr 245 250 255 His Gly Gly Gly Gly Gly Gly Gly Glu Ala Lys Asp Phe Leu Asp Met 260 265 270 Phe Leu Asp Ile Met Glu Ser Gly Lys Ala Glu Val Lys Phe Thr Arg 275 280 285 Glu His Leu Lys Ala Leu Ile Leu Asp Phe Phe Thr Ala Gly Thr Asp 290 295 300 Thr Thr Ala Ile Val Cys Glu Trp Ala Ile Ala Glu Val Ile Asn Asn 305 310 315 320 Pro Asn Val Leu Lys Lys Ala Gln Glu Glu Ile Ala Asn Ile Val Gly 325 330 335 Phe Asp Arg Ile Leu Gln Glu Ser Asp Ala Pro Asn Leu Pro Tyr Leu 340 345 350 Gln Ala Leu Ile Lys Glu Thr Phe Arg Leu His Pro Pro Ile Pro Met 355 360 365 Leu Ala Arg Lys Ser Ile Ser Asp Cys Val Ile Asp Gly Tyr Met Ile 370 375 380 Pro Ala Asn Thr Leu Leu Phe Val Asn Leu Trp Ser Met Gly Arg Asn 385 390 395 400 Pro Lys Ile Trp Asp Tyr Pro Thr Ala Phe Gln Pro Glu Arg Phe Leu 405 410 415 Glu Lys Glu Lys Ala Ala Ile Asp Val Lys Gly Gln His Phe Glu Leu 420 425 430 Leu Pro Phe Gly Thr Gly Arg Arg Gly Cys Pro Gly Met Leu Leu Ala 435 440 445 Ile Gln Glu Val Val Ile Ile Ile Gly Thr Met Ile Gln Cys Phe Asp 450 455 460 Trp Lys Leu Pro Asp Gly Ser Gly His Val Asp Met Ala Glu Arg Pro 465 470 475 480 Gly Leu Thr Ala Pro Arg Glu Thr Asp Leu Phe Cys Arg Val Val Pro 485 490 495 Arg Val Asp Pro Leu Val Val Ser Thr Gln 500 505 

What is claimed is:
 1. An isolated gene encoding a protein, wherein said protein has an activity of synthesizing flavones from flavanones, further wherein the protein has the amino acid sequence as shown in SEQ ID NO:
 4. 2. An isolated gene having the nucleotide sequence of SEQ ID NO:
 3. 3. A vector comprising the isolated gene according to claim
 1. 4. A plant host transformed by the vector according to claim
 3. 5. A method of producing a protein with flavone-synthesizing activity, comprising culturing or growing the plant host according to claim 4 and recovering said protein from said plant host.
 6. A plant into which the gene according to claim 1 has been introduced, or progenies of said plant or a tissue thereof having said gene.
 7. A cut flower from the plant or the progeny thereof according to claim
 6. 8. A method of altering a composition of flavonoids or amount thereof, or both the composition and amount in a plant host comprising introducing a vector having the gene according to claim 1 into a plant host; culturing or growing said plant host; and recovering flavones; wherein said flavones are included in a composition of flavonoids.
 9. The method according to claim 8, wherein said gene is inserted in the vector in the antisense direction.
 10. A method of altering the amount of a flavone in a plant host comprising introducing a vector having the gene according to claim 1 into a plant host; culturing or growing said plant host, wherein said flavone synthase gene is expressed and amount of flavone altered.
 11. The method according to claim 10, wherein said gene is inserted in the vector in the antisense direction.
 12. A method of altering the color of a flower comprising introducing a vector having the gene according to claim 1 into a flower plant; culturing or growing said plant, wherein said gene is expressed and expression of said gene alters the flower color in said plant.
 13. The method according to claim 12, wherein said gene is inserted in the vector in the antisense direction.
 14. A method of bluing the color of a flower comprising introducing a vector having the gene according to claim 1 into a flower plant; and culturing or growing said flower plant, wherein the gene is expressed and flavone is produced in the flower plant.
 15. A method of reddening the color of a flower comprising introducing a vector having the gene according to claim 1 inserted in the antisense direction into a flower plant; and culturing or growing said plant, wherein expression of the gene is suppressed in the flower plant.
 16. A method of altering the photosensitivity of a plant comprising introducing a vector having the gene according to claim 1 into a plant; and culturing or growing said plant, wherein the gene is expressed.
 17. A method of controlling the interaction between a plant and microorganisms comprising introducing a vector having the gene according to claim 1 into a plant and culturing or growing said plant, wherein the gene is expressed and flavone produced in the plant.
 18. A method of altering a composition of flavones or amount thereof, or both the composition and amount in a plant or tissue thereof comprising introducing a vector having the gene according to claim 1 into a plant or tissue thereof; and culturing or growing said plant or tissue, whereby the gene is expressed in said plant or tissue.
 19. The method according to claim 18, wherein said gene is inserted in the vector in the antisense direction.
 20. A method of suppressing flavone synthesis in a plant or tissue thereof, comprising introducing a vector having the gene according to claim 1 inserted in the antisense direction into a plant or tissue thereof; and culturing or growing said plant or tissue, whereby expression of the gene is suppressed in said plant.
 21. A method of increasing an amount of flavone in a flower petal, comprising introducing a vector having the gene according to claim 1 into a plant or tissue thereof; and culturing or growing said plant or tissue, whereby the gene is expressed in said plant.
 22. A method of decreasing an amount of flavone in a flower petal, comprising introducing a vector having the gene according to claim 1 inserted in the antisense direction into a plant or tissue thereof; and culturing or growing said plant or tissue, whereby expression of the gene is suppressed in said plant.
 23. A method of synthesizing a flavone from flavanone comprising introducing a vector having the gene according to claim 1 into a plant host having flavanones; culturing or growing said plant host, whereby said gene is expressed in said plant host to produce a flavone synthase; and said flavone synthase synthesizes flavone from said flavanone.
 24. A method for producing a flavone synthase comprising introducing a vector having the gene according to claim 1 into a plant host; culturing or growing said plant host, whereby said gene is expressed in said plant host to produce a flavone synthase. 